Anne's purpose was to one, let out all of her feelings, and if she lived, to show what terrible things the Nazis were doing to her.
It was showing them secrets, because she knew where they hid all of their weapons, and how they killed the Jewish people.
A single text can be used for many purposes. For example, if you read an article about sharks, you can get different ideas from it, like sharks are dangerous OR attacks can be provoked only by humans.
